The present invention relates to a direct sealing coupling which requires no sealing material such as a gasket and metal O- and C-rings.
With insertion of sealing material such as a gasket and metal O- and C-rings, large pipes are connected by a bolt and a nut with a flange, and relatively smaller pipes are connected with a female nut.
For example, FIG. 4 illustrates a known sealing coupling for connecting relatively smaller pipes with a female nut 101. A gasket 104 and an end portion 106 of a sleeve 105 are engaged in an annular groove 103 at the end of the body 102. Adjacent the end of the sleeve 106, a flange 107 is formed to encircle the sleeve 106, and a thrust bearing 108 is provided between the flange 107 and the female nut 101. A female thread 109 is formed on the inner surface of the female nut 101, and a male thread 110 on the outer surface of the body 102 is engaged with the female thread 109. To form sealing by connecting the sleeve 105 with the body 102, the female nut 101 is engaged with the body 102, so that force is applied to the flange 107 via the thrust bearing 108, and the gasket 104 is collapsed between the end faces of the sleeve 105 and the body 102, whereby sealing is formed.
However, there are disadvantages in the known art as follows:
a) With the gasket 105, there is unevenness at the connection of an opening 111 of the sleeve 105 and an opening 112 in the body 102, so that flow disturvance in the openings 111 and 112 occurs.
b) When a gasket is used, it would be partially pressed by strong force, and for preventing the gasket from falling, an overlapped portion is formed between the body and the sleeve.
c) When parts such as a sleeve and a body is taken out upwardly by removing a female nut, the body has to be forcedly separated from the sleeve until the overlapped portion of the body and the sleeve disappears, thereby causing damage to conduits connected to each.
d) When the coupling is disassembled, the gasket is liable to fall, and assembling is troublesome since a gasket and a retainer have to be installed.